【python学习记录2】Add Two Numbers

问题描述

You are given two linked lists representing two non-negative numbers. The digits are stored in reverse order and each of their nodes contain a single digit. Add the two numbers and return it as a linked list.
Input: (2 -> 4 -> 3) + (5 -> 6 -> 4)
Output: 7 -> 0 -> 8

详细问题

代码实现

# Definition for singly-linked list.
# class ListNode(object):
#     def __init__(self, x):
#         self.val = x
#         self.next = None

class Solution(object):
    def addTwoNumbers(self, l1, l2):
        """
        :type l1: ListNode
        :type l2: ListNode
        :rtype: ListNode
        """
        headNode = ListNode(0)
        point = headNode
        sum = 0
        while (l1 != None) or (l2 != None) :
            if(l1 != None) :
                sum = sum + l1.val
                l1 = l1.next
            if(l2 != None) :
                sum = sum + l2.val
                l2 = l2.next
            newNode = ListNode(sum % 10)
            point.next = newNode
            point = point.next
            sum = sum//10
        if sum > 0 :
            newNode = ListNode(sum)
            point.next = newNode
        return headNode.next

经验总结

• 定义新的头结点（headNode）有利于返回和控制整个链表
• 两个if判断是否为None，简化了代码结构，避免了多次分类讨论
• 临时变量定义新sum，随机记录